Ligand-Assisted Extraction of Metals from Fly Ash with Supercritical CO2: A Comparison with Extraction in Aqueous and Organic Solutions

Three different techniques were applied for the aqueous extraction of anions from coal and fly ash: rotary mixer- and ultrasonic-assisted extraction with different duration time, and microwave-assisted extraction at different temperatures. Validation showed that the ion-chromatographic method was suitable for the analysis of anions in coal and fly ash extracts. The variations in the amounts of anions using different extraction times during rotary-assisted extraction were minimal for all investigated anions. The efficiency of ultrasound-assisted extraction of anions from coal depended on the sonication time and was highest at 30 min. The ultrasound-assisted extraction was less efficient for the extraction of anions from fly ash than rotary-assisted extraction. Increase of temperature in the microwave-assisted extraction had a positive effect on the amounts of all anions extracted from coal and sulphate from fly ash, while the amounts of fluoride and chloride in fly ash extracts decreased. The microwave-assisted extraction of coal at 150?C was compared with standard ASTM methods, and results were in good agreement only for chloride. Changes in the pH value and conductivity during ultrasound-assisted extraction were measured in order to explain changes on the surface of coal particles in contact with water and different processes that occur under environmental conditions.

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Application of water as a solvent in microwave-assisted extraction for analysis of PCBs and CBzs in fly ash

Journal of Separation Science ◽

10.1002/jssc.200401860 ◽

2005 ◽

Vol 28 (6) ◽

pp. 585-588 ◽

Cited By ~ 23

Author(s):

Yifei Sun ◽

Masaki Takaoka ◽

Nobuo Takeda ◽

Tadao Matsumoto ◽

Kazuyuki Oshita

Keyword(s):

Fly Ash ◽

Microwave Assisted Extraction ◽

Microwave Assisted ◽

Assisted Extraction

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Sequestration of supercritical CO2 by mercury oxide

Chemical Papers ◽

10.2478/s11696-013-0356-2 ◽

2013 ◽

Vol 67 (6) ◽

Cited By ~ 3

Author(s):

Kledi Xhaxhiu ◽

Erisa Saraçi ◽

Klaus Bente

Keyword(s):

Fly Ash ◽

Binary System ◽

Flue Gas ◽

Supercritical Co2 ◽

Power Plants ◽

Laboratory Method ◽

Mercury Oxide ◽

Permanent Fixation ◽

Waste Incinerators ◽

Geological Formations

AbstractHgCO3·2HgO (mercury oxide carbonate), along with partly unreacted reactants, was obtained by exploring the behaviour of the Hg2Cl2/HgO binary system in supercritical CO2 (scCO2) at 200°C, 22000 kPa in the presence and absence of water, using a self-made laboratory-scale system. The reaction of pure HgO with scCO2 aimed at the synthesis of HgCO3 (mercury carbonate), also yielded the same product. Meanwhile, with a small amount of water present in the Hg2Cl2/HgO-scCO2 system, at 200°C, 22000 kPa, the mineral terlinguaite (Hg4O2Cl2) was obtained instead of mercury oxide carbonate. Repeating this reaction under the same conditions, but in the absence of CO2, again resulted in the synthesis of terlinguaite, leading to the assumption that the scCO2 had no influence on the synthesis of terlinguaite. This study reveals a new moisture-free laboratory method and conditions for the permanent fixation of CO2 by HgO. This method bears two benefits: 1) it can be introduced to reduce the Hg content in flue gas and fly ash emitted from coal-burning power plants and municipal waste incinerators; 2) it can contribute to CO2 mineralisation in montroydite (HgO) geological formations as mercury oxide carbonate.

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Enhanced Electrokinetic Removal of Heavy Metals in MSWI Fly Ash Assisted by Cation Exchange Membranes

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.84-85.626 ◽

2011 ◽

Vol 84-85 ◽

pp. 626-630 ◽

Cited By ~ 3

Author(s):

Xi Peng ◽

Bin Quan Jiao ◽

Lin Yu ◽

Dong Wei Li ◽

Ke Yang

Keyword(s):

Heavy Metals ◽

Fly Ash ◽

Cation Exchange ◽

Electroosmotic Flow ◽

Metal Extraction ◽

Mswi Fly Ash ◽

Assisted Extraction ◽

Removal Of Heavy Metals ◽

Trial Test ◽

Exchange Membrane

Since MSWI fly ash enriches heavy metals and many toxic components and these components would potentially leach when the ashes are land filled, it is regulated as hazardous waste in many countries. Electrokinetic removal, an electrochemically assisted extraction method, has recently been adopted as a new method for removal of heavy metals from MSWI fly ashes. But the generation of metal hydroxide precipitation near the cathode decreased conductivity of electrokinetic removal system and limited metal extraction from the sample area. In this study, cation exchange membrane was used in electrokinetic removal experiment to improve this method. After 192 hours of electrokinetic removal, about 15%Cd,20%Pb, 30% Zn, and 10% As was removed from 2.850kg MSWI fly ash. It showed positive effect compared to the trial test. But there still exists some problems, such as low removal efficiency. Further work should be done to solve it.Moreover, the high conductivity in fly ash limits the current , which in turn causes low electroosmotic flow. While electroosmotic flow is the main factor leting the heavy meatals release from fly ash, it would become the focus in further experiment to look for ways increasing the electroosmotic flow in sample cell.

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